Carbon circuit breaker



Nov. 22, 1955 Filed Dec. 26, 1952 w. F. MORGAN 2,724,755

CARBON CIRCUIT BREAKER 2 Sheets-Sheet l 1 V 0 1.111115 VI/( M W yINVENTOR.

WILLIAM F. MORGAN ATTORNEY Nov. 22, 1955 w. F. MORGAN 2,724,755

CARBON CIRCUIT BREAKER Filed Dec. 26, 1952 2 Sheets-Sheet 2 C53 50V, DC

WILLIAM F. MORGAN ATTORNEY States Patent CARBON CIRCUIT BREAKER WilliamF. Morgan, Johnson City, N. Y., assignor to International BusinessMachines fiorporation, New York, N. Y., a corporation of New YorkApplication December 26, 1952, Serial No. 327,975

12 Claims. (Cl. 29(l145) This invention relates to circuit interruptingapparatus and more particularly to circuit breakers of the multiple p ypAn object of the invention is to provide improved circuit interruptermeans.

Another object of the invention is to furnish improved circuit breakermeans of the carbon pile type capable of interrupting highly inductivecurrent loads with sharp cut-off characteristics.

Another object is to furnish an improved circuit breaker means of thestacked carbon type capable of interrupting highly inductive directcurrent loads over a wide range of current values with substantially thesame cut-ofi. characteristics.

Still another object of the invention is to provide a stacked disccircuit breaker in which the wear on the discs is evenly distributedthroughout the contact surfaces thereof.

A further object of this invention is to produce a carbon pile circuitbreaker for highly inductive current loads which exhibits low energyarcing and small induced peak voltages.

A still further object of the instant invention is to furnish a carbonpile circuit breaker which includes one or more metallic contactsassociated therewith and which exhibits long wearing characteristics inhigh speed operation over sustained periods of time.

Another object of this invention is to provide a carbon pile circuitbreaker in which wearing of the contact surfaces may be quickly andsimply compensated for without removing or replacing the carbon pile.

Still another object of the invention is to provide improved circuitbreaker means as aforementioned which is simple in construction andeconomical in manufacture.

Other objects of the invention will be pointed out in the followingdescription and claims and illustrated in the accompanying drawings,which disclose, by way of examples, the principle of the invention andthe best mode, which has been contemplated, of applying that principle.

in the drawings:

Fig. l is a side elevation of one embodiment of the present invention;

Fig. 2 is an enlarged sectional view taken on lines 2-2 of Fig. 1;

Fig. 3 is an exploded view of a portion of the embodiment shown in Fig.1;

Fig. 4 is a side elevation of the carbon pile showing another embodimentthereof including a pair of tungsten contacts;

Fig. 5 is a side elevation of the carbon pile showing still anotherembodiment thereof including a plurality of pairs of tungsten contacts;

Fig. 6 is a schematic circuit in which the instant invention may beplaced to provide efficient circuit break-' ing characteristics;

Fig. 7 is a timing chart for the circuit breakers shown in Fig. 6;

ice

Fig. 8 shows at a a sample current waveform for one operation of thecircuit breaker and at b shows the voltage waveform associatedtherewith; and

Fig. 9 shows at a sample current waveforms for dif ferent current valuesand at b shows the voltage waveforms associated therewith.

Similar reference characters represent similar parts throughout theseveral views.

Much difliculty has been encountered in D. C. circuit breakers whichcarry highly inductive current loads where the current varies over awide range of values. In breaking a highly inductive circuit peakvoltages in the order of eight-hundred volts or more are oftenencountered and the faster the break is made the higher the peakvoltage. In order to preserve the breaker contacts it is desirable tobreak the circuit as quickly as possible with minimum arcing. It is alsodesirable to maintain substantially the same cut-off characteristicsover a wide range of currents, for example, between Zero and sixtyamperes. This is necessary to preserve the timing of the device withwhich the circuit breaker is used. The present invention overcomes theseditficulties in a manner which will be obvious from the followingdetailed description.

Referring to Figs. 1, 2 and 3 of the drawings, one embodiment of thecircuit breaker forming the instant invention is shown. The circuitbreaker includes a frame member It? for holding the circuit interruptingelements. A lip 11 is formed at one corner of the frame, said lip beingprovided with a tapped aperture for receiving an adjusting screw 12. Ahanger or mounting member 13 is slotted as at 14 to receive screws i5which secure the hanger to the frame member. Adjustment of the framewith respect to the hanger may be made by adjusting screw 12. The hangeris also provided with apertures 16 which may be utilized in mounting thehanger to the device with which the circuit breaker is to be used. Aconnecting screw 17 is provided on the free end of the hanger, therebyforming a terminal to which one side of the circuit is connected. Boththe frame and hanger are constructed of a material having electricalconducting properties.

The carbon pile assembly, illustrated generally by reference numeral 18,comprises a plurality of carbon discs 19 mounted in stacked relation toeach other. As used herein, the term carbon is meant to include carbonand graphitic materials or mixtures of other materials in combinationtherewith. Each of the discs is undercut as at 20, the arrangement ofdiscs being such that the undercut side of one disc is next to the flatside of an adjacent disc. Each disc is provided with a centrallyarranged aperture 21 which is adapted to slidably receive a nylonplunger 22. Frame 10 is also apertured as at 23 to slidably receive saidplunger. A metallic plate 24 is mounted adjacent the top disc of thecarbon pile, said plate being provided with a centrally arrangeddownwardly extending sleeve 26 which is internally threaded to receive athreaded reduced portion 25 of plunger 22. The shoulder 27 formed bysaid reduced portion is adapted to abut an insulating Washer 28 which inturn abuts the lower end of sleeve 26 and the bottom surface of the topcarbon disc. In this manner the top disc is firmly secured to themetallic plate. A washer type finger spring 29 is apertured to slidablyreceive said plunger and is mounted between the aforementioned washerand the undercut portion of the disc which is adjacent the top disc.Spring 29 is constructed such that a base portion 30 is formed whichabuts the carbon disc. A plurality of spirally arranged fingers 31extend from said base portion, said fingers having rounded surfaces 31aon the ends thereof adapted to contact said washer.

Between the remaining discs insulating washers 32 and springs 29 areprovided, there being one washer and one spring fitted into the undercutportion of each of the discs.

The only difference between washers 32 and washer 28 is the differencein aperture size.

The top of frame It is furnished with a threaded aperture 36 adapted toreceive an externally threaded sleeve 41, said sleeve having a flange 42secured to the lower end thereof. Flange 42 is knurled on the peripherythereof to aid in rotating the sleeve in the frame aperture. Aninsulating sleeve 43 is mounted inside sleeve 41, said insulating sleeveprojecting beyond the upper end of sleeve 41.

A bolt 35 is adapted to be slidably received by sleeve 43, said boltbeing provided with spaced head members 33 and 34. A washer type fingerspring, illustrated generally by reference numeral 37, is mountedbetween said head members and plate 24. The purpose of this spring is tocompress the carbon pile and to provide a good electrical conductor.Spring 37 has an apertured central por tion 38, which fits between saidhead members, and a pair of fingers 39, the ends of said fingers beingriveted, as at 40, to plate 24. the junction of said fingers with saidapertured central portion which add endurance to the spring. Aninsulating washer 45 is mounted between flange 42 and head member 33.

In securing bolt 35 in place an insulating washer 46 is mounted on theprojecting end of sleeve 43 and a nut 47 is threaded on said bolt. Thenut may be tightened until the bolt is firmly secured. Bolt 335 performsan additional function of acting as the other terminal of the circuitbreaker. An additional nut 48 is provided for securing an electricallead to the bolt.

From the above detailed description it will be seen that an electriccircuit is formed from terminal 17, through hanger 13, frame 10, carbonpile 13, plate 24, spring 39 and bolt 35.

As is well known the resistance of the carbon pile changes with appliedpressure. Spring 39 is utilized to compress the carbon pile to providelow resistance to the current flow.

In order to break the circuit it is necessary to relieve the pressureapplied to the carbon pile by spring 39. When this occurs springs 29tend to separate the carbon discs, thereby increasing the resistance toinfinity. The pressure is relieved by compressing spring 39 throughmovement of plunger 22. While the plunger may be moved in a variety ofways the particular structure shown for causing the movement is in theform of a cam and cam follower arrangement. The cam follower,illustrated generally by reference numeral 48, includes a cam followerarm 51 and cam follower rollers 52, said cam follower arm beingpivotally mounted by pin 49 on frame bracket 50. The free end of the camfollower arm is bifurcated to receive a guide post 53, said post beingutilized to prevent lateral movement of the arm. Rollers 52 are adaptedto ride on the cam 54. it will be understood that the instant cam whichis shown is only by way of example, the shape thereof being dependent onthe timing cycle required. When rollers 52 ride on the low dwell 55 ofthe cam the circuit is closed and when the rollers ride on the highdwell 56 the circuit is open. That is, movement of the rollers from thelow dwell to the high dwell causes the cam follower arm to engageplunger 22 and move it upwardly. As the plunger begins its movement,plate 24 and the upper carbon disc are moved therewith, the movement ofthe plate relieving the pressure on the carbon pile. At this timesprings 29 between the discs tend to separate all of the discs, therebyincreasing the resistance in the pile to infinity. The rise inresistance from a very low resistance to infinity, from the instant theplunger begins its movement, is very rapid but not instantaneous, as inthe case of conventional circuit breakers.

The washer type finger springs between adjacent discs perform a veryuseful function. When pressure is applied to the stack the fingers arecompressed. As the pres- Raised surfaces 44 are provided near sure isremoved the fingersmove the adjacent discs axially of the plunger toseparate the contacting surfaces.

It will be noted that when springs 29 are compressed, the ends of thefingers thereof are angularly displaced. The friction between the endsof the fingers, the insulatin washers, and the carbon discs, causes thediscs to rotate as said angular displacement occurs. The bottom discadjacent the frame does not rotate due to friction therebetween. Arelative motion does exist between all discs. The result of the discrotation is a smooth contacting surface upon which the wear has beenevenly distributed.

Wear on the carbon discs tends to change the timing of the break point.That is, as the discs become thinner, plunger 22 is moved further downtowards the cam follower. This causes the break point to advance to someextent, thereby upsetting the timing cycle of the device. A certainamount of the carbon pile wear is compensated for by mechanical wear onthe end of the plunger, on the cam follower, and the cam itself. Anadjustment may be made simply by loosening screws 15, adjusting screw12, and then tightening screws 15. It is but necessary to use a feelergauge between plunger 22 and the cam follower arm to make a preciseadjustment which will restore the original timing condition.

The amount of pressure applied to the pile may be varied by rotatingknurled flange 42. As the wear on the carbon pile increases over a longperiod of time the pressure applied thereto decreases. Therefore it isnecessary to move flange 4-2 so that the pressure on the pile isincreased.

The present invention is particularly useful as a D.-C. impulse circuitbreaker, where, for example, the circuit is broken as many as sixtytimes per second and greater, on highly inductive current loads. As anexample, the instant invention may be used in a circuit such as thatshownin Fig. 6, a representative cam timing chart of which is shown inFig. 7. As shown, circuit breakers CB-1 and CB-2 are connected inparallel and circuit breakers CB-3 and CB-4 are also connected inparallel.

Circuit breaker CB-4, in the instant circuit, is the carbon pile circuitbreaker, CB3 being used as a shunting circuit breaker. The pairs ofcircuit breakers are series connccted and act as the switching meansbetween the input D. C. voltage and the inductive load. As shown in thetiming chart CB3 makes ahead of CB-4, which in turn makes ahead of theremaining circuit breakers. CB-l and CB-Z are make circuit breakerswhile CB-4 isthe break circuit breaker. CB-1 and CB-2 close at the sametime thereby completing the circuit. After approximately 6 from the timethe circuit is closed CB-3 opens. The circuit is broken when CB-4 opens3 after CB-3 opened. in this manner the full current load passes throughthe carbon pile only for the 3 duration after CB-3 opens.

Sample wave forms are shown in Figs. 8 and 9 for the circuit shown. Fig.8 shows at a the current curve 57. The current builds up upon completionof the circuit and comes to a high point which lasts a few degrees. WhenCB-3 opens the full load of the circuit passes through the carbon pile.Since the resistance of the carbon pile amounts to approximatelytwo-tenths ohms the current drops slightly forming a clip 58 which lastsfor approximately 3. At cut-off the current drops sharply to the zeroline. The dip below the zero line is due to the capacitor.

The voltage curve shown at b, illustrated by reference numeral 59, showsthat when the circuit is broken the voltage across the circuit breakerremains at approximately fifty volts, the D. C. input voltage. As thecircuit is made and the current builds up, the voltage across thecontacts drops to zero and stays at this level until the circuit isbroken. At this time the voltage peaks sharply to approximately onehundred and fifty volts, as at 60, and then drops substantiallyexponentially to the: fifty volt level. The ability of the carbon pileto continuously increase its resistance as the pressure is relievedprevents an instantaneous interruption of current, thereby decreasingthe self-induced peak voltage. Thus, it is possible to prevent the peakvoltage from reaching such high values as one thousand volts or greater.The particular wave forms shown were obtained from an oscilloscopeconnected in the circuit after the circuit had been made and broken overone-half billion times on a six ampere highly inductive load having anR/L ratio of approximately 200 with fifty volts D. C. applied.

In Fig. 9, at a current wave forms 61 and 62 show the currentcharacteristics for a six ampere and a sixty ampere load, respectively.The voltage curves associated with wave forms 61 and 62 are shown at b.It will be noted that cut-oif is made in substantially the same periodof time under both current load conditions. This is very advantageoussince the timing of the circuit is not upset over varying current loads.

When the circuit breaker forming the present invention is operated atvery high speeds separation occurs between the top two carbon discsbefore it occurs between the remaining discs. Under very high loads suchaction causes proportionally more wear on the top two discs.

A study of the action of the carbon pile in breaking the circuit willreveal the reason why the early separation occurs. When plunger 22 ismoved axially of the discs its movement is positive. The plunger carriesthe plate 24 and the top carbon disc with it. The spring action betweenthe discs is not sufficiently strong to overcome the inertia thereof andmove as fast as the aforementioned top disc and plate. Therefore, thetop disc moves away from the disc adjacent thereto and then theremaining discs separate. Under slower speeds this condition does notprevail to as great an extent since the springs 29 can overcome theinertia of the aforementioned remaining discs as fast as the cam movesthe top disc upwardly.

A modification of the present invention proposes to replace the carboncontacting surfaces of the top two carbon discs with a metallic surface.As shown in Fig. 4, the top two discs 63 and 64 have been reduced insize insofar as their carbon thickness is concerned. Metallic rings 65constructed of a contact material such as tungsten, are welded to thereduced thickness carbon discs, the overall thickness of eachtungsten-carbon disc being equal to the thickness of the normal carbondisc 19. The tungsten surfaces are mounted in contacting relation.

' Whenever high speed operation causes the top two discs to separatefirst, the tungsten is utilized to withstand arcing thereacross. Whilearcing causes tungsten to wear away faster than carbon in terms of unitweight, the density of tungsten is so much greater that the wear on thesurface is less. In this manner the early arcing between the top twodiscs is taken advantage of by providing contact materials capable ofabsorbing much more arcing with less wear, thereby saving wear on theremaining discs which are made of carbon only. With a six ampere loadhaving an R/L ratio as previously mentioned, the total wear on thecarbon pile of this construction after two-hundred million operationswas only seven-thousandths of an inch, with the cam and circuit usedthis Wear corresponded to a one degree change in timing.

Where the speed of operation is relatively low and the discs allseparate quite evenly, the advantages of the abovementioned tungstencontacts may be obtained by additionally compressing the spring tendingto separate the tungsten surfaces. This may be accomplished merely byproviding a thicker insulating washer between the carbon discs havingthe tungsten Welded thereto. Thus, the additionally compressed springtends to separate the tungsten surfaces first permitting a majority ofthe arcing at this point. It has been found that most wear occurs on thetungsten ring which is positive with respect to the other ring.Advantage is taken of this fact by making the freely rotatable tungstendisc positive in order to distribute the wear evenly over the entiresurface. in view of this consideration, it is possible to make the fixeddisc of carbon or other softer and cheaper contact materials. Thus, itis necessary to provide only one disc having the tungsten ring.

A further modification is made in Fig. 5, wherein pairs of carbon discshaving tungsten rings welded thereto are utilized.- These pairs ofdiscs, illustrated gencombined carbon-tungsten disc.

erally by reference numeral 66, are each similar to the pair of discshaving reference numerals 63 and 64 shown in Fig. 4. Each pair of thediscs is separated by a carbon disc 67 which is one-half the thicknessof the As in the first two forms of the invention insulating washers andsprings are provided in the space formed between the pair of discs.

The advantage of using a circuit breaker such as that shown in Fig. 5 isextreme timing stability because the wear is confined solely to thetungsten surfaces. There is a sacrifice in circuit breakingcharacteristics on high loads, however, due to the decrease in thenumber of contact gaps. The number of flat carbon discs 67 is determinedby thickness and space considerations and they are used to obtain achange in resistance with a variation in pressure.

Overall advantages of the carbon pile forming the present invention aresmall size in relation to the current which it is capable ofinterrupting, high speed of operation, ability to dissipate much of thestored energy as heat rather than in destructive arcing, long life,reliability, and ease of adjustment to compensate for wear.

While there have been shown and described and point-- ed out thefundamental novel features of the invention as applied to a preferredembodiment, it will be understood that various omissions andsubstitutions and changes in the form and details of the deviceillustrated and in its operation may be made by those skilled in theart, without departing from the spirit of the invention. It is theintention, therefore, to be limited only as indicated by the scope ofthe following claims.

What is claimed is:

1. An electric circuit interrupter comprising a plurality of discs,means for mounting said discs in a freely rotatable stacked relation, atleast some of said discs being constructed of a material Whoseelectrical resistance varies with the pressure applied thereto, meansfor compressing said discs to establish an electric circuittherethrough, means operating on said compressing means for removing thepressure applied to said discs, and means mounted between at least twoof said discs for separating the contacting surfaces thereof and causingrelative rotation therebetween.

2. An electric circuit interrupter comprising a plurality of discs,means mounting said discs in stacked relation, at least some of saiddiscs being constructed of carbon, means for applying pressure to saiddiscs to establish an electric circuit therethrough, means operativelyconnected to the last named means for removing the pressure applied tosaid discs, and means mounted between certain of said discs forseparating the contacting surfaces thereof and causing unidirectionalrotational motion of at least one of said certain discs.

3. An electric circuit interrupter comprising a stack of carbon discs,at least some of said discs being mounted for unlimited rotation, meansengaging said stack of discs for applying a pressure thereto so as toestablish an electric circuit therethrough, actuating means connected tosaid last named means for removing the pressure applied to said stack,and means engaging at least some of said discs for separating thecontacting surfaces thereof and causing relative rotation therebetween.

4. A circuit breaker of the carbon pile type comprising a plurality ofcarbon discs, at least one of said discs having a metallic contactingsurface, means mounting said discs in stacked relation, means engagingthe stack of said discs for resiliently applying a pressure thereto toestablish an electric circuit therethrough, means endiscs, said springmeans applying a pressure to said stack.

of discs for establishing a circuit therethrough, means for relievingthe pressure onsaid carbonpile, and means mounted between said discs forseparating the contacting surfaces thereof to break the'circuit, saidlast. named means causing relative rotation between the contacting.

surfaces. of said. discs after said discs. have been. separated.

6. A carbon pile circuit breaker comprising a plurality of carbon discsmounted in stacked relation, spring means for applying a pressure tothe: stack of said discs and causing relative rotation between two ofsaid discs, and actuating means operatively associated withsaid lastnamed means for removing the pressure from said discs and separatingthecontacting surfaces of the aforementioned discs having relativerotation.

7. A carbon pile circuit breaker comprising a plurality of carbon discsmounted in stacked relation, means for applying a pressure to the stackof said discs and causing relative rotation between two of said discs,and actuating means operatively associated with said last named meansfor removing the pressure from said discs and separating the contactingsurfaces of the aforementioned discs havingrelative rotation, at leastone of saiddiscs havingv relativev rotation being constructed to have ametallic contact surface.

8.. A carbon pile circuit breaker comprising-a: plurality of freelyrotatable discs mounted in stacked relation, at least some of said discsbeing constructed of carbon, means for applying a pressure to. thestackof said discs and causing" relative rotation between two of saiddiscs, and actuating means operatively associated with said last namedmeans for removing the pressure from. said discs and separating thecontacting surfaces of the aforementioned discs having. relativerotation.

9. A carbon'pile circuit breaker comprising a plurality of discs atleast some of which-are constructed of carbon, said discs being mountedin stacked relation, means operatively engaging the stack of said discsfor applying: a.

pressure thereto, and means for removing the. pressure from said discs,one of said discs being connected to one of said. means to causeseparation betweensaid one disc and the remaining discs after saidpressure isremoved,

and means between a plurality of the remaining discs for causingseparation between the contacting surfaces thereof after separationbetween. said onev disc and the remaining discs.

10. A carbon pile circuit breaker comprising a plurality of discs atleast some of which are constructed of. carbon, said discs being mountedin. stacked relation, means operatively engaging the stack of said discsfor applying a pressure. thereto, and means for removingthe pressurefrom said discs, one of said discs being related to the last named meansto cause separation between said one:

disc and the remaining discs after said pressure is removed, at leastone of the separating surfaces between said one disc and said remainingdiscs being of ametallic contact material, and means between a pluralityof the remaining discs for causing separation between the contactingsurfaces thereof after separation between said. one disc and theremaining discs.

11. A carbon pile circuit breaker'comprising a plurality of carbon discsmounted in stacked relation,.rneansopera-- tively engaging the stack ofsaid discs for applying apressure thereto so that the contactingsurfaces thereof are in engagement, means for removing the pressure fromsaid stack of discs, at least one pair of said. discs having tungstenwelded thereto to form the only contacting surfaces therebetween.

12. A carbon pile circuit breaker comprising a plurality of carbon discsmounted in stacked relation, means operatively engaging the stack ofsaid discsfor applying a pressure thereto,-..means for removing thepressure from saidstack of discs, at least one pair ofv said discshaving tungsten welded thereto to form the contacting surfacestherebetween, and. means operatively engaging said pair of discs forseparating the contacting surfaces thereof and causing. relativerotation therebetweenafter said separation occurs so that differentportions of the contacting surfaces are moved into engagement when.engagement again occurs.

References Cited in the file of this patent UNITED STATES PATENTS1,216,386 Williams et al Feb; 20, 1917 1,817,155 Leece Aug. 4, 1931'1,839,629 Williams Jan. 5', 1932 1,873,499 Steinmayer Aug. 23', 19321,900,236 Hall Mar. 7 1933' 1,984,947 Schweibold Dec. 18, 1934 2,026,405Thompson Dec. 31, 1935 2,406,449 'Whittaker Aug. 27, I946 FOREIGNPATENTS 470,875 Great Britain Ang.124, 1937

